1. Field of the Invention
This invention relates generally to a printing apparatus in which sheets of paper successively removed from a stack thereof are printed while individually wrapped about a rotatable platen, and the invention is more particularly directed to a paper feeding and ejecting device for such apparatus.
2. Description of the Prior Art
In an existing paper feeding and ejecting device for a printing apparatus, a rotatable platen has a cutout extending across a peripheral surface to define a chucking seat, and a gripping assembly for securing on such seat the leading end portion of a paper sheet manually fed to the platen over a support plate extending to the surface of the platen at the top of the latter. After a sheet of paper has been thus fed to the platen, a push-button is actuated to provide a printing command signal by which the gripping assembly is made operative to secure the leading end of the sheet to the platen at the chucking seat of the latter, and the platen is rotated in one direction for winding or wrapping the sheet thereon. During such rotation of the platen, the sheet wrapped thereon is carried past a printing position at which, for example, a thermal head acts on the paper sheet through an interposed ink sheet or web for effecting thermal printing of the paper sheet on the platen. Upon completion of the printing operation, the paper gripping assembly is moved to its released position, and the platen is rotated for ejecting the printed paper sheet therefrom. Finally, the ejected paper sheet is manually removed from the printing apparatus.
In the above described existing paper feeding and ejecting device for a printing apparatus, the paper feeding and ejecting involve manual operations, and, therefore, are relatively troublesome and not uniformly effected. Further, since the paper feeding and ejecting occur through the same guide passage, the reduction of the time required for a complete printing cycle is limited in that the paper sheet to be printed can be inserted into the guide passage only after a previously printed paper sheet has been fully ejected or removed from such passage.
Consideration has been given, by persons having an obligation of assignment to the owner of the present invention at the time the latter was made, to overcoming the previously stated problems by providing apparatus including separate paper feeding and ejecting guide passages, a paper feeding device automatically operative to feed paper to be printed through the feeding guide passage to the rotary platen, and a paper ejecting device by which the paper which has been printed is automatically ejected through the ejecting guide passage. In such apparatus having separate paper feeding and ejecting guide passages, two separate motors have been required for driving the paper feeding device and the paper ejecting device, respectively, independently of each other, and this results in undesirable complications and relatively high cost of the apparatus. Further, when the paper to be printed is automatically fed by a paper feeding device in the form of a roller, the apparatus is susceptible to jamming by reason of inaccurate timing of the operation of the paper feeding device relative to other operations of the apparatus, such as, rotation of the platen in the course of a printing operation. In order to avoid the undesirable consequences of timing errors, additional sensors are required for accurately controlling successive movements of the paper feeding device, but this also results in an undesirably complicated structure of relatively high cost.